The cost of installing a historic sewer system in a new parcel of land is one of the largest roadblocks to economic and infrastructure development for any community. Similarly, small or remote communities cannot afford the high price of adding a historic sewer system even for residential usage and citizens continue to use private wells and inefficient septic systems.
Historic sewer system installations cause significant disruption to a community and require major reconstruction of roadways. Individual dwellings are connected to a historic sewer system through the use of large diameter rigid piping consisting of a series of interconnecting pipe. The connections of such pipes are not sealed, allowing infiltration of ground water which can account for 50% to 70% of a historic sewage system's capacity. These unsealed locations along the collection mains and laterals can also result in exfiltration of sewage effluent which can be as high as 30% to 40% of the sewage effluent passing through the system.
Historic sewer systems typically use jointed PVC tubing which averages 200 mm to 600 mm in diameter. Rubber gaskets, prone to degradation and leaking are typically used at the connections. Over time, the pipes of such systems flex unduly and/or are subject to tree root intrusion and as a result, pipes can separate, resulting in infiltration of ground water into the sewer system.
Moreover, historic pipes must be deeply buried below frost penetration elevation. Therefore, historic sewer pipes require the digging of large, straight trenches approximately a minimum of 6 to 8 feet deep, sloping steeply at 0.5%. As well, the preferred and normal location of historic systems is below the roadway centerline. Historic sewers therefore are timely to install and the choice of overall layout is dictated by access for maintenance.
In addition, historic systems are sensitive to gradient changes. Pipe gradients are steeper than the road gradients to allow for the required higher scouring velocities required to cleanse wastewater solids. Historic pipes are kept in a straight alignment between manholes to aid maintenance and cleaning of the system.
The inclusion of ground water and high peaking factors in the design of pipes, pump stations, and treatment plants can result in an overall historic sewer system which is complex and oversized. Historic sewer systems collect solid waste sludge at the treatment plants which must be removed regularly. Due to limited storage capacity at plants, sludge is kept for a short time in the system, and there is little degradation of sludge; therefore, high sludge volumes result from the lack of sufficient sludge digestion time.
Lift pumps must be correspondingly large and complex in order to handle solids and high peak flows.
Other more efficient sewer systems, such as U.S. Pat. No. 5,895,569 to Connelly, have overcome the problems of historic sewer systems. Connelly discloses watertight pipes downstream of the primary treatment unit. Connelly, however, does not disclose a zero water infiltration or sewage exfiltration system. Furthermore, Connelly does not disclose means to optimize the amount of total suspended solids (TSS) which is retained in the first compartment of the primary treatment unit.
Therefore, there is a need to provide a new efficient sewer collection system for residential buildings which is inexpensive to install and maintain and which overcomes the problems identified in the prior art.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.